linux-kernel - Re: [PATCH] IB/ehca: Serialize HCA-related hCalls on POWER5

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Date:	Sun, 09 Dec 2007 15:22:39 -0800
From:	Roland Dreier <rdreier@...co.com>
To:	Arnd Bergmann <arnd@...db.de>
Cc:	linuxppc-dev@...abs.org, Joachim Fenkes <fenkes@...ibm.com>,
	LKML <linux-kernel@...r.kernel.org>,
	OF-EWG <ewg@...ts.openfabrics.org>,
	Christoph Raisch <raisch@...ibm.com>,
	Marcus Eder <meder@...ibm.com>,
	OF-General <general@...ts.openfabrics.org>,
	Stefan Roscher <stefan.roscher@...ibm.com>
Subject: Re: [PATCH] IB/ehca: Serialize HCA-related hCalls on POWER5

 > I think it needs some more inspection. The msleep in there is only called
 > for hcalls that return H_IS_LONG_BUSY(). In theory, you can call
 > ehca_plpar_hcall_norets() from inside an interrupt handler if the
 > hcall in question never returns long busy.

Fair enough... according to Documentation/infiniband/core_locking.txt,
the only driver methods that cannot sleep are:

    create_ah
    modify_ah
    query_ah
    destroy_ah
    bind_mw
    post_send
    post_recv
    poll_cq
    req_notify_cq
    map_phys_fmr

and I don't think ehca does an hcall from any of those.  Of course
there might be other driver-internal code paths that I don't know
about.  Maybe do a quick audit and then stick might_sleep() in the
hcall functions to catch any mistakes?

 - R.
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